This invention relates to lasers and more particularly to a high power gas transport laser having a plurality of sets of electrodes.
A CO.sub.2 gas transport laser that has been built and successfully used for producing continuous wave output power in the order of 1 and 2 KW is described in U.S. Pat. No. 3,772,610. Wide industrial application of such a laser has resulted in a need for higher output powers, i.e., in the order of 5 KW and above and to meet this need, two laser units of the type described in the foregoing patent have been connected in tandem with the optical axes of the units in alignment; the reflecting mirrors are mounted on the outer side walls of the units and the inner side walls have an opening through which the generated laser beam passes. A single high power beam is thus generated by connecting two separate laser apparatuses together in optical series.
The technique for starting the laser as described in the above patent is mounting a starter electrode close to the cathode and connecting that electrode to the source of anode voltage. As the voltage between cathode and anode is raised in order to start the discharge, a small discharge first forms between the starter electrode and the cathode. As the voltage is raised further, ions generated by this small discharge initiate the main discharge between cathode and the several resistively ballasted anode pads. At this point, the voltage immediately drops due to the addition of the much lower impedance path of the main discharge. Without this initial "starter" discharge, the voltage required to initiate the main discharge is very high.
While this starting technique works well with a single laser unit, it does not perform satisfactorily with two such units having cathodes electrically connected in parallel as required with the 5 KW laser. As the voltage is raised to initiate a two-cathode discharge, one cathode discharge invariably starts first due to unavoidable impedance differences of the two units. Thereafer, because the voltage immediately decreases as described above, the second cathode discharge is unable to start.
This invention is directed to a solution of this problem.
An object of the invention is the provision of apparatus for initiating the discharge of a gas transport laser having two or more sets of electrodes.
A further object is the provision of a method of starting the discharge of a gas transport laser having two or more sets of electrodes.
These and other objects of the invention are achieved with a circuit for and a method of applying a pulse or pulses of energy simultaneously to one electrode of each set of electrodes while a DC potential is applied across those electrodes.